1. Technical Field
The present invention relates to an amplifier, and more particularly, to an amplifier that detects a predetermined degree of excessive input and controls attenuation of an input signal.
2. Background Art
Conventionally, an amplitude limiter circuit is sometimes used for output of an amplifier or inside of a circuit of the amplifier in order not to supply excessive input to an apparatus connected to an output side of the amplifier (see JP-A-2002-368563, for example).
The amplitude limiter circuit, because of limiting the peak value of an output signal, allows preventing the apparatus connected to the output side of the amplifier from being broken by excessive input.
However, in the conventional art, when the amplitude of an input signal increases over a level at which limitation in amplitude is started, the output signal waveform of the amplifier is clipped. When the amplitude of an input signal further increases, the distortion factor of an output signal increases therewith, and the output signal waveform approximates a square wave. When the output signal waveform then becomes a square wave, two times as much as an applied power becomes necessary for the amplifier to supply an output signal to the subsequent apparatus, as compared to that in the case of sine waves where the output signal waveform is not clipped.